1. Technical Field
This invention relates to containers and closures therefore designed to indicate the removal of the closure so that the purchaser may be assured that the contents of the container are as originally packed.
2. Description of Prior Art
Prior art containers and closures, for example, milk bottles require a closure which tightly seals the opening of the container to prevent leakage of the contents therein. A typical container has a threaded neck with a horizontal radially inturned directed annular flange at the top of the neck which defines the opening to the container. A typical threaded closure for use therewith is shown in U.S. Pat. No. 3,504,818 in which a closure formed of resilient flexible plastic material is disclosed for use on a blow molded flexible plastic bottle.
Another prior art disclosure comprises U.S. Pat. No. 3,902,621 which is similar to the closure of U.S. Pat. No. 3,504,818 with the exception that the annular tamper indicator ring is separated and an elongated pull tab extends outwardly so as to connect the ends of the tamper indicating ring.
A still further prior art disclosure comprises U.S. Pat. No. 4,498,597 wherein the container has a threaded neck portion and a flexible lip portion which extends inwardly and upwardly from the top of the neck portion.
Each of these prior art references and many similar closures incorporating threaded neck portions and threaded closures for registry therewith have the common fault of a so-called initial loosening of the closure once it has been threaded onto the container neck as the prior art threaded closures engageable on threaded necks of containers relied on increased friction between the engaging threads of the closure and the threads of the neck portion to hold the closure in sealed position on the neck portion of the container. Such containers and closures are generally made of resilient flexible plastic material and distortion or changes in the tension on the closure and neck portion frequently causes a loosening of the closure as the closure backs off slightly from its turned on initial position on the neck portion and this slight movement frequently results in leakage of the contents of the container. None of the prior art devices have been able to control such initial changes in the position of the closure relative to the threaded neck portion and the actual cause of such reverse rotation of the closure is unknown.
The present invention provides a simple efficient and novel means of substantially increasing and controlling the frictional engagement of the threads in the closure with the threads on the threaded neck portion of the container by forming the threads on the neck portion of the container with a surface area larger than the surface area of the threads in the closure and forming a plurality of radially upwardly extending small ribs on the upper smaller surface area of the threads on the interior of the closure and a similar series of radially downwardly extending small ribs on the larger lower surface area of the threads on the threaded neck of the container. The small ribs are on the smaller engaging surfaces of the threads of the closure and the larger threads on the threaded neck portion in effect form very desirable special limited roughened surfaces which substantially hold the closure in its initial turned on position relative to the neck portion of the container and prevents counter rotation as above described which leads to looseness of the closure and leakage of the contents of the container and at the same time ensures against too much thread to thread locking action.